Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly=false, destructive=false, openWorld=true, so the safety profile is covered. The description adds the valuable constraint that credentials and autopilot are out of scope, but says nothing about partial-update behavior (all six params are optional), permissions, or what a successful change returns.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short sentences, editable scope front-loaded before the exclusion, zero filler. The phrase 'stay in the app' is slightly colloquial where 'must be changed in the app' would be unambiguous, but nothing is wasted.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a six-parameter mutation with no annotations gaps and no output schema, the description covers scope and exclusions but leaves the key operational question unanswered: whether omitted fields are left untouched or cleared. Partial-update semantics matter a lot for a sparse-update tool and are absent.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With only 50% schema coverage, the description does real work: it groups all six parameters into four user-facing concepts (name, phone, language→locale, app appearance→ui_theme/ui_font_scale/narration_enabled). It could be sharper—'app appearance' is a loose umbrella for narration_enabled, a workout-behavior flag rather than visual styling.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (changes) and a specific resource (the trainer's own profile), then enumerates the editable facets: name, phone, language, app appearance. The possessive 'the trainer's' plus the name make it distinguishable from update_student and update_public_profile without opening the schema, though neither sibling is named.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Provides a useful exclusion ('E-mail, password and autopilot stay in the app'), which tells the agent what not to attempt here. However, it never routes to alternatives: no mention that public-facing data belongs to update_public_profile, or that reading current values should use get_my_profile.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.